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Magnetismus Donnerstag<br />

resonante Mode auf, bei der die Position des Vortex auf einer Kreisbahn<br />

um den Mittelpunkt der Kreisscheibe mit der Frequenz des angelegten<br />

Felds rotiert [2]. Bei höherer Frequenz von ca. 5 GHz enteht eine resonante<br />

Mode anderen Typs, bei der stehende Wellen innerhalb der Kreisscheibe<br />

angeregt werden. [1] A. Wachowiak et al., Science 298, (5593)<br />

577 (2002) [2] Guslienko et al., J. Appl. Phys. 91 (10) 8037 (2002)<br />

MA 28.5 Do 16:15 H23<br />

Spin Dynamics in Permalloy Disks with Vortex Structure<br />

— •Matthias Buess 1,2 , Rainer Höllinger 1 , Thomas<br />

Haug 1 , Korbinian Perzlmaier 1 , Michael R. Scheinfein<br />

3 , Danilo Pescia 2 , and Christian H. Back 1 — 1 Institut<br />

fürExperimentelle und Angewandte Physik, Universität Regensburg,<br />

Universitätsstrasse 31, 93040 Regensburg, Germany — 2 Laboratorium<br />

für Festkörperphysik,Eidgenössische Technische Hochschule Zürich,<br />

CH-8093Zürich,Switzerland — 3 Simon Fraser University, 8888 University<br />

Drive, Burnaby BC U5A 156, Canada<br />

Micron sized ferromagnetic permalloy disks exhibiting a ferromagnetic<br />

vortex structure are excited by a magnetic field pulse. The fast rise time<br />

pulse field is generated by an optically triggered electrical pulse in a lithographically<br />

fabricated microcoil. The excitation is imaged using time resolved<br />

magneto-optic polar Kerr microscopy - a stroboscopic experiment.<br />

We present the spatially resolved magnetic maps at different delay times,<br />

stitched together to form a magnetic movie. The dynamical excitations<br />

are composed of symmetric and non-sysmmetric parts which can not be<br />

separated at first glance. However, in the Fourier transformation of the<br />

magnetic movie we identify several modes which can be accounted for<br />

in a simple model based on purely dipolar interactions. The model is<br />

supported by micromagnetic simulations and shows good quantitative<br />

agreement in the resonance frequencies for different modes and sample<br />

dimensions.<br />

MA 28.6 Do 16:30 H23<br />

NANOSECOND TIME-SCALE SWITCHING OF THIN FILM<br />

PERMALLOY ELEMENTS — •Dmitry Chumakov, Rudolf<br />

Schäfer, Jeffrey McCord, and Ludwig Schultz — IFW-Dresden,<br />

Helmholtzstr. 20, D-01069 Dresden, Germany<br />

We have studied the dynamic magnetization switching behaviour of<br />

thin film Permalloy elements by gated ICCD camera-based time-resolved<br />

wide-field Kerr microscopy. The structures were subject to pulsed magnetic<br />

fields of different strengths from 1600 A/m to 5200 A/m. Their<br />

reversal was observed with 250 ps time-resolution. By interpreting the<br />

experimental results we point out the peculiarities of the nanosecond<br />

timescale switching. Like in the quasistatic case, the dynamic remagnetization<br />

process is dominated by the generation of concertina-like domain<br />

patterns. Whereas such ”blocked” domains decay irreversibly in several<br />

steps during quasistatic switching, the blocking is resolved by continuous<br />

rotation in a locally inhomogeneous way for dynamic switching. This<br />

process lasts several nanoseconds and leads to significant delays in element<br />

switching. The influence of magnetic field amplitude, rise-time,<br />

and element shape on the switching behaviour will be shown at various<br />

examples.<br />

MA 28.7 Do 16:45 H23<br />

Magnetization Dynamics of Micron Sized Permalloy Squares —<br />

•Korbinian Perzlmaier, Christian Back, Matthias Buess, and<br />

Rainer Höllinger — Institut für Experimentelle und Angewandte<br />

Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg<br />

We investigate the dynamic response of the magnetization in micron<br />

sized Permalloy squares by measuring the polar Kerr component in a<br />

time resolved Kerr-microscope. The sample is excited with a fast rise<br />

time magnetic field pulse (typically pulse fields are smaller than 100 Oe)<br />

applied perpendicular to the sample plane. Magnetic movies are recorded<br />

with a frame rate of 10 ps. From the Fourier transform of the data we<br />

obtain information about the modal frequencies.<br />

Numerical methods based on the LLG equation are commonly used<br />

to simulate the dynamic response of magnetic elements. We extract the<br />

modal structure from simulated movies of squares in the size range between<br />

300 nm and 4 micron. The results are compared to our experiments.<br />

MA 28.8 Do 17:00 H23<br />

Investigation of magnetization dynamics of microstructured<br />

magnetic thin films by means of Time-Resolved Photoemission<br />

Electron Microscopy. — •A. Krasyuk 1 , A. Oelsner 1 , S.A.<br />

Nepijko 1 , D. Neeb 1 , A. Kuksov 2 , C.M. Schneider 2 und G.<br />

Schönhense 1 — 1 Johannes Gutenberg-Universität Mainz, Institut<br />

für Physik, Staudinger Weg 7, 55099 Mainz, Germany — 2 Institut für<br />

Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany<br />

The magnetisation reversal dynamics of the lithographically prepared<br />

Permalloy particles with different forms and thickness ranging from<br />

10nm up to 40nm was observed exploiting the Magnetic X-Ray Circular<br />

Dichroism (MXCD) contrast at the Ni L3 X-ray absorption edges in subns<br />

range by means Time-Resolved Photoemission Electron Microscope.<br />

The experiment has been performed in single-bunch mode at the BESSY<br />

II (Berlin) and 16-bunch mode at the ESRF (Grenoble). [1] A. Krasyuk,<br />

A. Oelsner, S.A. Nepijko, A. Kuksov, C.M. Schneider, G. Schönhense.,<br />

Appl.Phys.A, 2003, 76, No.6, 863-868. [2] A. Oelsner, A. Krasyuk, D.<br />

Neeb, S.A. Nepijko, A. Kuksov, C.M. Schneider, G. Schönhense., J. Electr.<br />

Spectr. Rel. Phenom, accepted<br />

MA 28.9 Do 17:15 H23<br />

Damping in thin NiFe films — •Hans Nembach, Markus C. Weber,<br />

Jürgen Fassbender, and Burkard Hillebrands — Fachbereich<br />

Physik und Forschungsschwerpunkt MINAS, Technische Universität<br />

Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663 Kaiserslautern<br />

We investigated the damping and spin wave creation in thin NiFe films<br />

with time-resolved magneto-optic Kerr effect magnetometry for small and<br />

large angle excitations. To gain further insight in the underlying damping<br />

process we employ a special measurement procedure, which allows<br />

us to determine all three magnetization vector components and therefore<br />

the length of the magnetization vector. A reduction of the magnitude<br />

of the magnetization vector indicates the creation of spin waves. These<br />

spin waves can be created directly by the stripline or by multi-magnon<br />

processes.<br />

The experimentally determined magnetization trajectory is compared<br />

with numerical simulations based on the Landau-Lifshitz equation, and<br />

the damping constant is extracted from these simulations<br />

MA 28.10 Do 17:30 H23<br />

Dependence of magnetization reversal dynamics on magnetic<br />

anisotropy and interlayer coupling — •K. Fukumoto 1 , W.<br />

Kuch 1 , J. Vogel 2 , J. Camarero 3 , S. Pizzini 2 , Y. Pennec 2 ,<br />

F. Offi 1 , M. Bonfim 4 , A. Fontaine 2 , and J. Kirschner 1 —<br />

1 Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120<br />

Halle, Germany — 2 Laboratoire Louis Néel, CNRS, 25 Avenue des<br />

Martyrs, B. P. 166, F-38042 Grenoble Cedex 9, France — 3 Dpto. Física<br />

de la Materia Condensada, Universidad Autónoma de Madrid, E-28049<br />

Madrid, Spain — 4 Departamento de Engenharia Elètrica, Universidade<br />

do Paraná, CEP 81531-990, Curitiba, Brazil<br />

Time- and element-resolved magnetic domain imaging measurements<br />

were performed using x-ray magnetic circular dichroism photoelectron<br />

emission microscopy (XMCD-PEEM). Two types of spin-valve-like samples<br />

(Fe20Ni80/Cu/Co) were used in this study, one with and one without<br />

magnetic anisotropy in the film plane. Magnetization reversal during<br />

nanosecond-short magnetic field pulses was investigated by a pumpprobe<br />

technique. Domain wall motion induced by the field pulses (pump)<br />

was imaged using photon pulses from single bunch operation of BESSY<br />

(probe). Magnetization reversal and domain structure of the permalloy<br />

layer in the sample showing no anisotropy in the plane are strongly influenced<br />

by local pinning. In the sample with in-plane anisotropy, domain<br />

patterns during the reversal of the permalloy layer are less reproducible,<br />

and more influenced by the local coupling with the Co layer. Reversal<br />

mechanism, speed of domain wall motion, and the effect of magnetic<br />

interlayer coupling were also studied using single-pulse measurements.<br />

MA 28.11 Do 17:45 H23<br />

All optical probe of coherent spin waves in exchange bias<br />

systems — •B. Beschoten 1 , A. Tillmanns 1 , S. Oertker 1 , G.<br />

Güntherodt 1 , I.K. Schuller 2 , C. Leighton 3 , and J. Nogués 4<br />

— 1 2. Physikalisches Institut, RWTH Aachen, 52056 Aachen —<br />

2 Department of Physics, UC San Diego — 3 Department of Chemical<br />

Engineering and Materials Science, University of Minnesota —<br />

4 Departament de Fisica, Universitat Autònoma de Barcelona<br />

Time-resolved Kerr rotation is used to generate and to probe coherent<br />

spin waves in exchange biased ferro-/antiferromagnetic bilayer films of

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